Yes. Adding extension tubes behind a pinhole body cap increases the pinhole-to-sensor distance, which effectively gives a longer focal length and a narrower angle of view. It also reduces the light reaching the sensor, so exposures get much longer.

The main drawback is image quality: a pinhole size that works well at one distance is not necessarily optimal at a longer distance. As you extend the tube, the ideal pinhole would usually need to be larger, so using the same body-cap pinhole can become suboptimal. Very long exposures may also introduce more sensor noise.

It’s still a perfectly valid experiment, and many people make simple test versions with extension tubes, cardboard tubes, aluminum foil, and a carefully made hole. A practical approach is to start with a short distance, test results, then increase the extension and compare sharpness and exposure time. Make sure any extension tubes fit your Nikon F-mount camera.